AUTOMATED ANALYSIS OF BAUXITE EXPLORATION DRILL HOLE SAMPLES BY DIFFUSE REFLECTANCE – FOURIER-TRANSFORM INFRARED (FTIR) SPECTROSCOPY

Unprecedented world demand for alumina has resulted in production expansion programs at several alumina refineries. The subsequent escalation in bauxite exploration programs has intensified demand for routine bauxite analysis. In the case of the Suralco laboratory, expansion of the Suralco-BHP Billiton Joint Venture bauxite exploration program has translated to an additional 3,000 samples per week.

Conventional methods of analysis, such as wet chemical digestion and x-ray fluorescence techniques would require approximately thirty days to analyse 3,000 samples. To achieve such an anticipated increase in analytical throughput with these methods, expansion of the laboratory together with additional equipment and manpower would be required.

Bauxite analysis by Fourier-Transform Infrared (FTIR) spectroscopy is an established Alcoa method for the routine analysis for Darling Range (Western Australia) bauxite. FTIR provides a nondestructive, simultaneous and fast means of analysis without the need for wet chemical or fusion methods of analysis, except those required for calibration and routine check analysis (typically 1% of throughput).

Fully automated FTIR analysers have been installed and commissioned in both Suralco and Jamalco laboratories. Automation is accomplished using a 6-axis robotic arm that can identify and prepare a sample from a vial, complete FTIR spectroscopic measurement, dispose of the waste bauxite and return vials for re-use with a cycle time of approximately 60 seconds. This provides an analytical throughput of approximately 1,400 samples per day with each sample being analysed for several components such as reactive silica, available alumina, total iron, total silica, total alumina and total titania. The Suralco laboratory has estimated that the cost of analysis has been reduced from US$2.50 to US$0.10 per sample.